Ultraviolet Radiation Induced DNA Damage in Bacterioplankton in the Southern Ocean

9419037杰弗里现在有强有力的证据表明，在地球表面的某些地方紫外线辐射正在增加。主要关注的是南极洲和南大洋臭氧消耗的年度模式，与臭氧空洞事件前相比，那里的臭氧水平下降了74%。平流层臭氧浓度的降低已被证明会导致紫外线辐射水平的增加。臭氧消耗导致的紫外线辐射增加对浮游植物和初级生产力的影响已经引起了广泛的兴趣，而对细菌的影响在很大程度上被忽视了。从以前在南大洋和其他地方的研究中可以明显看出，细菌在营养物质矿化过程中发挥着至关重要的作用，并为高等生物提供了营养纽带。本研究的目的是确定由紫外线辐射和臭氧消耗引起的浮游细菌的DNA损伤，将DNA修复基因(RecA)的诱导强度与损伤的程度联系起来，并估计压力对通过细菌组合的碳通量的影响。分子生物学在鉴定光产物和研究细胞DNA修复机制诱导方面的敏感新进展将与测量细菌生物量和产量的传统方法相结合。嘧啶-嘧啶酮(6-4)光产物和环丁烷二聚体是紫外光照射下产生的独特的光产物。这些DNA损伤可以用放射免疫分析来识别。RecA基因在细菌中分布广泛且高度保守。由于该基因在DNA损伤修复中起着关键作用，其浓度和活性将被用来直接检测细菌对DNA损伤的反应。通过对细菌生物量、产量和生长效率的测量，将估计对细菌碳通量的细微影响。这一结果将提供有关浮游生物中紫外线诱导的分子损伤量和修复机制的信息。紫外线-A辐射和紫外线-B辐射都会造成细胞损伤，而只有紫外线-B辐射会因臭氧消耗而增强。通过同时分析DNA损伤和诱导recA基因作为对损伤的一般反应，将紫外线-B辐射的效果与其他DNA损伤机制进行对比。将提供更多关于对总产量的影响的信息，并进一步阐明南大洋细菌和浮游植物产量之间的相互作用。

9419037 Jeffrey There is now strong evidence that ultraviolet radiation is increasing over certain locations on the Earth's surface. Of primary concern has been the annual pattern of ozone depletion over Antarctica and the Southern Ocean where ozone levels have declined as much as 74% compared to pre-ozone hole events. Reduction of ozone concentration in the stratosphere has been shown to result in an increase levels of ultraviolet radiation. The impact of increased ultraviolet radiation due to ozone depletion upon phytoplankton and primary production has received extensive interest, while the effects on bacteria have been largely overlooked. It is apparent from previous studies in both the Southern Ocean and elsewhere that bacteria play a vital role in mineralization of nutrients and provide a trophic link to higher organisms. The objectives of this study are identify DNA damage in bacterioplankton resulting from ultraviolet radiation and as a function of ozone depletion, relate the intensity of the induction of DNA repair genes (recA) to the extent of damage, and estimate the effect of the stress on carbon fluxes through bacterial assemblages. Sensitive new advances in molecular biology to identify photoproducts and examine the induction of cellular DNA repair mechanisms will be coupled with traditional approaches for measuring bacterial biomass and production. Pyrimidine-pyrimidone (6-4) photoproducts and cyclobutane dimers are the unique photoproducts created by ultraviolet radiation. These DNA lesions may be identified using radioimmunoassays. The recA gene is wide spread and highly conserved among bacteria. Because of the pivotal role of this gene in repairing damaged DNA, its concentration and activity will be used as a direct assay of the bacterial response to DNA damage. With measurements of bacterial biomass, production and growth efficiency, subtle effects on bacterial carbon fluxes will be estimated. The results will provide information on the amount of UV induced molecular damage and repair mechanisms in planktonic populations. Both ultraviolet-A radiation and ultraviolet-B radiation create cellular damage, while only ultraviolet-B radiation is enhanced as a result of ozone depletion. Through simultaneous analysis of DNA damage and the induction of the recA gene as a general response to damage, the effect of ultraviolet-B radiation will be contrasted with other mechanisms of DNA damage. Additional information will be provided on the effects on total production and further elucidate the interactions of bacteria and phytoplankton production in the Southern Ocean.